Let's use this thread to convert Farland 3.5 magic items to 4E. Converted items should retain the flavor of the original, but no attempt need be made to match exactly.

Here's an attempt at the Crossbow of Wawmar

Original 3.5 item

Crossbow of Wawmar

Crafted under the hammers of the most expert metalsmiths in the world, the dwarves of Wawmar, this steel +3 heavy crossbow cannot be broken in battle or under normal use, although it is not indestructible (it can be destroyed in a normal forge). If the total number rolled to hit is 4 above the target's AC, then the opponent must save vs. will at DC 15 or be held as per a hold person spell cast by a 12th level caster. This power functions three times per day.

Weapon: Crossbow
Enhancement: Attack rolls and damage rolls
Critical: +1d6 damage per plus
Power (Daily): Free Action. Use this power when you hit with this weapon. The target is immobilized until the end of your next turn.

I based it off a level 2 item, the Resounding weapon, that dazes until the end of the turn. I think dazing is potentially more powerful. It is a daily power. I think making it have a save makes it potentially more powerful-- it could last longer. That was my reasoning. See any flaws?